A pudding served up cold (5)
I believe the answer is:
aloof
'cold' is the definition.
(both can mean distant)
'a pudding served up' is the wordplay.
'pudding' becomes 'fool' (type of dessert).
'served up' says the letters should be written backwards (in a down clue, letters go up).
'fool' back-to-front is 'loof'.
'a'+'loof'='ALOOF'
(Other definitions for aloof that I've seen before include "Socially detached" , "Indifferent - by oneself" , "Remote in manner" , "Coldly distant" , "Displaying supercilious reserve" .)